The aim of this research is to study the structure and function of four membrane transporters and enzymes. The overall objective is to understand how these proteins are arranged in the membrane, how they catalyze the reactions, how the activities of the proteins are regulated, and the tissue distribution of the various proteins. The questions concerning the (Na,K)ATPase are the function of the beta chain, the mechanism of regulation of the enzyme, and the significance of the two transcripts of the alpha 2 chain. The structure of the chloride channel of the electroplax of the ray is of interest to determine if it similar to or different from that of other chloride transporters, and whether a similar channel is present in skeletal muscle and is the main conductance pathway in resting muscle. The function of the ectonucleotidase, discovered in rat hepatocytes, will be explored through studies of the active site of the enzyme, the arrangement of the enzyme in T-tubule membranes and in the brush border of colon cells, and by determining whether a similar enzyme is present in yeast cells. The ATP transporter of chromaffin granules will be characterized with the view of determining whether or not this transporter is similar to the mitochondrial ATP/ADP translocase, and is present in the plasma membrane of cells.